Session Item

Salvage radiotherapy (SRT) is the main approach for early biochemical relapse (BR) after radical prostatectomy (RP). However, 68Ga-PSMA-11 PET/CT implementation in this setting prompted significant changes in current management of patients, leading to the development of imaging-guided approaches. In our department, a prospective study aimed to explore the outcomes after 68Ga-PSMA-11 PET/CT restaging and pre-defined treatment is currently running. Here we present early results of the first cohort enrolled, focusing on 68Ga-PSMA-11 PET/CT detection rate and following approach.

PSICHE (NCT05022914) is a prospective observational multicenter study including patients treated with RP +/- postoperative prostate bed radiotherapy, affected by BR (defined as PSA >0.2 ng/ml) with a PSA at recurrence <1 ng/ml. Patients are staged with centralized 68Ga-PSMA PET/CT and treated with a pre-defined approach based on 68Ga-PSMA PET/CT findings. Briefly, patients with negative 68Ga-PSMA PET/CT or positive findings within prostate bed are treated with prostate bed RT (or observation if postoperative RT already administered), pelvic nodal recurrence (defined as nodal disease <2 cm under aortic bifurcation) and oligometastatic disease (defined as defined as ≤3 non visceral metastatic lesions, according to Association of Radiotherapy and Clinical Oncology definition) are treated with stereotactic body radiotherapy (SBRT) to all positive sites of disease. Non oligometastatic disease (>3 lesions or visceral metastases) is treated with androgen deprivation therapy +/- other systemic therapies available for metastatic hormone sensitive prostate cancer, at physician discretion. All doses and fractionations allowed are pre-specified. Complete protocol details are available on clinicaltrials.gov .

Enrollment started on 19/03/2021. Up to date, 38 patients have been enrolled (Table 1). Median PSA triggering PSMA re-staging was 0.36 ng/ml. Overall, PSMA results were negative/positive in prostate bed in 26 patients (68.4%), while pelvic nodal or extrapelvic metastatic disease was detected in 11 (28.9%) and 1 (2.7%) patients, respectively. After re-staging, 14 patients (36.8%) had prostate bed RT, 12 (31.6%) underwent SBRT on pelvic nodal relapse and 1 patient (2.7%) was treated with SBRT to extrapelvic disease. 11 patients with negative staging previously received prostate bed RT, and underwent observation only after re-staging. No significant impact of PSA at recurrence or time to relapse (defined as time between surgery and BR) was detected on PSMA PET/CT detection rate (p=0.1 and p=0.43, respectively). ISUP ≤ or > 3 and D’amico risk category (low/intermediate vs high) had no influence or PSMA detection rate (p=0.36 and p=0.52, respectively).

Early results from PSICHE trial showed that macroscopic disease is detected in a significant percentage of patients affected by early BR. PSMA staging is necessary in this setting to avoid undertreatment and allow tailored treatment.